Thermionic valve



April 10, 1928. 1,665,626

H. ST. J. DE A. DONISTHORPE THERMIONIC VALVE Filed Oct. '1, 1922 Fig. 1

svwento'c HORACE STJOHN deAULA DONISTHQRPE 661 his Patented Apr. 10.1928.

UNITED STATES PATENT OFFICE.

HORACE ST. JOHN 1m AULA IDONISTHOBPE, or LONDON, ENGLAND, ASSIGNOR roRADIO coEroaArroN or AMERICA, A CORPORATION or DELAWARE.

THERMIONIC VALVE.

Application filed October 7, 1922, Serial No. 593,140, and in GreatBritain October 24, 1921. i

In a thermionic valve of the type wherein the cathode filament issurrounded wholly or partially by an anode which is open at its ends,the transfer of electrons from cathode to .anode has hitherto beenattended by considerable wastage or non-utilization of the electronsnear the open ends of the anode on account of the divergence of thepaths of the electrons due to their mutual repulsion.

The object of this invention is to prevent this wastage of electrons andthereby considerably to increase the efficiency of thermionic valves ofthe above mentioned type and also to prevent the portions of the glassenvelope of the valve which are opposite to the open ends of the anodefrom being bombarded. My invention is illustrated in the accompanyingdrawing, in which Fig. 1 shows one form of my improved valveand Fig. 2shows a modification of my improved valve. 7

According to this invention I provide means for energizing a helicalgrid 1 interposed between the anode 3 and the cathode 2 so that it willproduce a magnetic field which will counteract the etlect of mutualrepulsion on the electrons emitted near the ends of the cathode 2 andthereby hinder them from escaping through the open ends of the anode 3.I

Two methods of arranging the helical grid so that it will fulfill theabove mentioned function will be described. a

In the first method the grid 1 is wound uniformly in one directlon andits two ends are connected to the positive terminal of the battery 4while its middle point is connected through a variable resistance 5 tothe negative terminal of the said battery, so that each half willproduce a magnetic field which will attract inwards the electrons at theextremities of the rid but these fields will neutralize one anot er atthe middle of the grid.

In the second method, the helical grid 1 is wound, one half in onedirection and the other half in the opposite direction and the ends ofthe grid are connected respectively to the positive and negativeterminals of a battery 4 through a variable resistance 5 so thatmagnetic fields are produced of a similar nature to those of the firstmethod.

l/Vhile I have described above a certain theory for the operation ofthis invention, it is to be understood that I am not relying upon suchtheory, but that the same is offered merely to assist in the explanationof this invention.

. Having now described my invention, I declare that what I claim is:

1. A thermionic valve comprising a cathode, an anode, and a doubleterminal helical grid interposed between said cathode and said anode,said grid being constructed to produce a magnetic field of the samepolarity at opposite ends thereof.

2. A thermionic valve comprising a cathode, an anode, and a doubleterminal helical grid, said grid being adapted to be traversed by anelectric current whereby to produce a magnetic field thereabout, andsaid helical grid being formed to produce said magnetic field withmaximum intensity at opposite ends thereof and with minimum intensityalong a portion intermediate of the ends thereof.

3. A thermionic valve comprising a filamentary cathode, a grid helicallywound around said cathode, an anode surrounding said grid,' terminals onopposite ends of said grid, and a single terminal connected to said gridintermediate of said first mentioned terminals, whereby said grid may beconnected to a source of E. M. F. to permit current to flow throughseparate portions ofsaid grid and in opposite directions.

4. A thermionic valve comprising a cathode, an anode, and a doubleterminal helical grid, said grid being divided into two portions at apoint intermediate the ends thereof, a terminal carried by said grid atsaid point of division, and separate terminals on opposite ends of saidgrid, whereby said portions may be connected to a common source of E. M.F.in parallel relation to each other.

HORACE sr. JOHN a; hunt nomsrnoarr.

